From time to time there arises a need to effect mixing of the contents of containers such as cans and, in particular, aerosol cans. This mixing may be desired, for example, soon after the containers have been filled by filling equipment in a production line wherein the containers are conveyed by conveyors through various stations including a filling station as well as other stations such as, for example, a coating station, capping station, labelling station, etc. One technique for mixing the contents of the closed containers has been to manually shake the container or turn the container end over end. Also known is a rotary mixing device wherein the containers are manually loaded into a cradle which is then driven by a motor to rotate the containers end over end. The containers are held in the cradle in two rows parallel and symmetric to the rotational axis of the cradle. This mixing device, however, is only semi-automatic in that the containers must be manually loaded into and unloaded from the cradle.